Hydraulically-actuated vct system including a spool valve

ABSTRACT

A hydraulically-actuated variable camshaft timing (VCT) system comprises a spool valve including a sleeve and a spool, having a plurality of radially-outwardly extending lands, received within the sleeve; a first fluid supply port in the sleeve configured to receive fluid from a fluid supply; a second fluid supply port in the sleeve configured to receive fluid from the fluid supply; an advancing port in the sleeve in fluid communication with an advancing chamber of a hydraulically-actuated camshaft phaser; a retarding port in the sleeve in fluid communication with a retarding chamber of the hydraulically-actuated camshaft phaser; and an exhaust port axially positioned in the sleeve in between the first fluid supply port and the second fluid supply port or in between the advancing port and the retarding port, wherein the exhaust port is configured to selectively receive fluid from either the advancing chamber or the retarding chamber depending on an axial position of the spool relative to the sleeve.

The present application relates to fluid control and, more particularly, to linearly-moving spool valves that control the flow of fluid in a hydraulically-actuated VCT system.

BACKGROUND

Internal Combustion Engines (ICEs) selectively control the flow of fluid in a variety of ways. ICEs can use spool valves that include a sleeve and a spool having lands that slides linearly within the sleeve to selectively permit and stop the flow of fluid, such as engine oil. There are a number of different applications for a spool valve on an ICE, such as controlling the flow of fluid to a hydraulically-actuated variable camshaft timing (VCT) device—often referred to as a camshaft phaser. The spool includes one or more lands, positioned at precise axial locations along the spool, that extend radially-outwardly from an elongated body to engage a radially-inwardly-facing surface of the sleeve forming a fluid-tight seal. As the spool is moved linearly relative to the sleeve, the lands move as well, exposing different fluid pathways to communicate fluid from a source to the exposed fluid pathways. Flow through the fluid pathways can be controlled by moving the lands relative to the sleeve to expose or cover fluid ports in the sleeve that provide access to the fluid pathways. However, location of a fluid supply port relative to fluid exit ports may involve performance challenges. Carefully arranging a fluid supply port relative to a fluid exhaust port can improve the performance of a spool valve.

SUMMARY

In one implementation, a hydraulically-actuated variable camshaft timing (VCT) system comprises a spool valve including a sleeve and a spool, having a plurality of radially-outwardly extending lands, received within the sleeve; a first fluid supply port in the sleeve configured to receive fluid from a fluid supply; a second fluid supply port in the sleeve configured to receive fluid from the fluid supply; an advancing port in the sleeve in fluid communication with an advancing chamber of a hydraulically-actuated camshaft phaser; a retarding port in the sleeve in fluid communication with a retarding chamber of the hydraulically-actuated camshaft phaser; and an exhaust port axially positioned in the sleeve in between the first fluid supply port and the second fluid supply port or in between the advancing port and the retarding port, wherein the exhaust port is configured to selectively receive fluid from either the advancing chamber or the retarding chamber depending on an axial position of the spool relative to the sleeve.

In another implementation, a hydraulically-actuated variable VCT system, comprising: a spool valve including a sleeve and a spool, having a plurality of radially-outwardly extending lands and a spool cavity, received within the sleeve; a first fluid supply port in the sleeve configured to receive fluid from a fluid supply; a second fluid supply port in the sleeve configured to receive fluid from the fluid supply; and a spool exhaust port included with the spool cavity that is positioned axially between the first fluid supply port and the second fluid supply port, wherein the spool exhaust port and the spool cavity are configured to selectively receive fluid from an advancing chamber of a hydraulically-actuated camshaft phaser or a retarding chamber the hydraulically-actuated camshaft phaser.

In yet another implementation, a hydraulically-actuated VCT system, comprising: a spool valve including a sleeve and a spool, having a plurality of radially-outwardly extending lands, received within the sleeve; a first fluid supply port in the sleeve configured to receive fluid from a fluid supply; a second fluid supply port in the sleeve configured to receive fluid from the fluid supply; an advancing port in the sleeve configured to receive fluid from an advancing chamber of a hydraulically-actuated camshaft phaser; a retarding port in the sleeve configured to receive fluid from a retarding chamber of a hydraulically-actuated camshaft phaser; and an exhaust port axially positioned in the sleeve in between the first fluid supply port and the second fluid supply port, wherein the exhaust port is configured to receive fluid through either the advancing port or the retarding port depending on an axial position of the spool relative to the sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view depicting an implementation of a hydraulically-actuated variable camshaft timing (VCT) system;

FIG. 2 is a schematic view depicting an implementation of a hydraulically-actuated VCT system;

FIG. 3 is a schematic view depicting an implementation of a hydraulically-actuated VCT system;

FIG. 4 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 5 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 6 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 7 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 8 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 9 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 10 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 11 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 12 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 13 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 14 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 15 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 16A is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 16B is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 17 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 18 is a schematic view depicting another implementation of a hydraulically-actuated VCT system;

FIG. 19 is a schematic view depicting another implementation of a hydraulically-actuated VCT system; and

FIG. 20 is a schematic view depicting another implementation of a hydraulically-actuated VCT system.

DETAILED DESCRIPTION

A hydraulically-actuated VCT system has a spool valve that includes a spool sliding relative to a sleeve to control the flow of fluid from supply ports through a common exhaust port. In particular, a fluid exhaust port can be located axially along the sleeve in between a first fluid supply port and a second fluid supply port. In past spool valve implementations, fluid may be supplied at an axial end of the spool so that fluid flows axially and then radially outwardly from the axial center of the spool toward the sleeve. The fluid could then exit the phaser from different exhaust ports. However, in certain implementations, such as hydraulically-actuated variable camshaft timing (VCT) or cam phasers, axially positioning a common exhaust port along the length of the spool valve in between supply ports that exhaust fluid into the common exhaust port can increase the efficiency with which fluid is directed by venting fluid into the common exhaust port in the sleeve. Here, the supply ports can flow fluid radially with respect to the axis of spool movement. Fluid exiting advancing chambers or retarding chambers of the hydraulically-actuated phaser can each flow through the common exhaust port in the spool valve. Directing vented or exhaust fluid flow through the common exhaust port axially located between the fluid supply ports or axially located in between an advancing fluid pathway and a retarding fluid pathway can make it easier to recirculate the exhausted fluid to the hydraulically-actuated phaser or another desired location.

One implementation of a hydraulically-actuated variable camshaft timing (VCT) system 10 is shown in FIGS. 1-3. The system includes a hydraulically-actuated camshaft phaser 12, a spool valve 14 having a spool 16 and a sleeve 18, a pump 20 supplying pressurized fluid to the spool valve 14, and a fluid tank 22 that receives supplies fluid and receives exhaust fluid. The system 10 also includes a variable force solenoid (VFS) 24 that axially moves the spool 16 relative to the sleeve 18 in opposition to a spring 25 control the flow of fluid within the system 10. The phaser 12 includes a rotor 26 having, in this implementation, a plurality of vanes 28 that extend radially outwardly from a hub 30 and a stator housing 32 that receives the rotor 26. The vanes 28 can extend into fluid chambers 34 formed in the stator housing 32 separating the fluid chambers 34 into an advancing chamber 36 and a retarding chamber 38. An advancing fluid pathway 40 can fluidly communicate with the advancing chamber 36 while a retarding fluid pathway 42 can fluidly communicate with the retarding chamber 38. Flow of fluid into and out of the advancing fluid pathway 40 and the retarding fluid pathway 42 can exert force on the rotor 26 through the vanes 28, selectively rotating or holding the rotor 26 relative to the stator housing 32. An example of a hydraulically-actuated camshaft phaser is described in U.S. application Ser. No. 12/921,425 the contents of which are hereby incorporated by reference.

The rotor 26 can be mechanically attached to a camshaft by a fastener (not shown), such as a bolt, and the camshaft can be installed in the head of an internal combustion engine. A hydraulic lock 44 can be positioned in the stator housing 32 and be biased so that it releasably engages the rotor 26 to maintain a fixed angular position of the rotor 26 relative to the housing 32. The fluid pump 20 supplies pressurized fluid to the spool valve 14 through a first fluid supply 46 and a second fluid supply 48. The first fluid supply 46 and the second fluid supply 48 can each fluidly communicate with one or more ports or apertures in the sleeve 18 of the spool valve 14. For example, in this implementation, the first fluid supply 46 fluidly communicates supply fluid with a first fluid supply port 50 that receives fluid from the fluid pump 20. The second fluid supply 48 fluidly communicates fluid with a second fluid supply port 52. The first fluid supply port 50 and the second fluid supply port 52 are axially spaced apart on the sleeve 18 along the length of the sleeve 18. An exhaust port 54 can be axially positioned along the sleeve 18 in between the first fluid supply port 50 and the second fluid supply port 52. The advancing chamber 36 of the phaser 12 can be in fluid communication with the advancing fluid pathway 40 and an advancing port 56 formed in the sleeve 18 while the retarding chamber 38 can be in fluid communication with the retarding fluid pathway 42 and a retarding port 58. In some implementations, the exhaust port 54 can be positioned in between the advancing port 56 and the retarding port 58. Fluid can flow from the spool valve 14 through the advancing port 56 to the advancing chamber 36 or alternatively flow from the advancing chamber 36 through the advancing port 56 to the exhaust port 54. Similarly, fluid can flow from the spool valve 14 through the retarding port 58 to the retarding chamber 38 or alternatively flow from the retarding chamber 38 through the retarding port 58 to the exhaust port 54. This will be described below in more detail. The ports 54, 56, 58 can extend through the sleeve 18 between a sleeve cavity 60 radially inward of the sleeve and an outer surface of the sleeve 18. In this implementation, a check valve 62 can help control the flow of fluid from the fluid pump 20 to the first fluid supply port 50 and the second fluid supply port 52. Check valves can be implemented in any one of a variety of different ways. In this implementation, a ball check valve is shown but other check valves, such as reed valves, are also possible.

The spool 16 of the spool valve 14 is concentrically positioned relative to the sleeve 18 and is received within the sleeve cavity 60. The spool 16 includes an elongated body and a plurality of lands 64, located at axial positions along the body, that extend radially outwardly from the body. Radial outer surfaces 66 of the lands 64 have a shape corresponding to an inside surface of the sleeve cavity 60 such that the surfaces 66 of the lands 64 closely match the inside surface to prevent the axial flow of fluid from one side of the land 64 to another side of the land 64. In this implementation, the spool 16 includes four lands: two distal lands 64 a nearest the ends of the spool 16 that can prevent the escape of fluid from the spool valve 14 and two inner lands 64 b the axial movement of which directs fluid from the first fluid supply port 50 or the second fluid supply port 52 into the advancing port 56 and retarding port 58, respectively, as well as from the advancing and retarding ports 56, 58 into the exhaust port 54. The cross-sectional shape of the spool 16 and lands 64 can be annular or circular or another shape that conforms to an inner surface of the sleeve 18 within the sleeve cavity 60. Both the spool 16 and the lands 64 can be made from one many different types materials, such as a metal alloy. In this implementation, the first fluid supply port 50 can fluidly communicate with the advancing chamber 36 and the exhaust port 54 while the second fluid supply port 52 can fluidly communicate with the retarding chamber 38 and the exhaust port 54. That is, the exhaust port 54 can fluidly communicate with both the advancing port 56 and the retarding port 58 as well as with a reserve tank of fluid drawn on by the fluid pump.

Within the sleeve cavity 60, the spool 16 can slide axially relative to the sleeve 18 such that the axial position of the inner lands 64 b controls the flow between the fluid supply or pump 20 through the first fluid supply port 50, the second fluid supply port 52, the advancing port 56, the retarding port 58, and the exhaust port 54. This can be appreciated from FIGS. 1-3.

FIG. 1 depicts the system 10 positioning the spool 16 at a “fully withdrawn” position with respect to the sleeve 18. In this implementation, the fully withdrawn position of the spool 16 directs fluid from the advancing chamber 36 through the advancing port 56 to the exhaust port 54. The hydraulic lock 44 can be in fluid communication with the advancing port 56 and the fluid leaving the advancing chamber 36 through the advancing fluid pathway 40 can decrease the force overcoming a biasing spring of the lock 44 thereby permitting the lock 44 to engage the stator housing 32 and prevent rotational movement between the rotor 26 and the stator housing 32. The exhaust port 54 fluidly communicates the fluid leaving the advancing chamber 36 to the tank 22. Fluid from the fluid pump 20 passes through the check valve 62 to the second fluid supply port 52 where the inner land 64 b directs the fluid through the retarding port 58 to the retarding chamber 38.

Turning to FIG. 2, the spool 16 can be moved to a “mid position” where the inner lands 64 b prevent fluid from passing from the first fluid supply port 50 to the advancing port 56 or from the second supply port 52 to the retarding port 58. The mid position also can prevent fluid from exiting either the advancing chamber 36 or the retarding chamber 38 thereby maintaining the angular position of the rotor 26 relative to the stator housing 32. FIG. 3 depicts the system 10 positioning the spool 16 at a “fully inserted” position with respect to the sleeve 18. In this implementation, the fully inserted position of the spool 16 directs fluid from the fluid pump 20, passing through the check valve 62, to the first fluid supply port 50 where the inner land 64 b directs the fluid through the advancing port 56 to the advancing chamber 36. The hydraulic lock 44 can receive the fluid, which may overcome the force of the spring of the lock 44 thereby releasing the lock 44 from the stator housing 32 permitting rotational movement between the rotor 26 and the housing 32. Fluid from the retarding chamber 38 exits through the retarding port 58 to the exhaust port 54. The exhaust port 54 fluidly communicates the fluid leaving the advancing chamber 36 to the tank 22.

Turning now to FIG. 4, another implementation of a hydraulically-actuated VCT system 400 is shown. The system 400 includes the spool valve 14 having a spool 16′ that is concentrically positioned relative to the sleeve 18 and is received within the sleeve cavity 60. The spool 16′ includes an elongated body and a plurality of lands 64, located at axial positions along the body, that extend radially outwardly from the body. Radial outer surfaces 60 of the lands 64 have a shape corresponding to an inside surface of the sleeve cavity 60 such that the surface of the lands 64 closely matches the inside surface to prevent the axial flow of fluid from one side of the land to another side of the land. In this implementation, the spool 16′ includes four lands: two distal lands 64 a nearest the ends of the spool 16′ that can prevent the escape of fluid from the spool valve 14 and two inner lands 64 b the axial movement of which directs fluid from the first fluid supply port 50 or the second fluid supply port 52 into the advancing port 56 and retarding port 58, respectively, as well as from the advancing and retarding ports 56, 58 into the exhaust port 54. The spool 16′ includes a spool cavity 68 that is in fluid communication with the advancing port 56 and the retarding port 58 to receive fluid at an outer surface of the sleeve 18 and permits the fluid to flow axially from a spool exhaust port 78 in the spool cavity 68 to a distal exhaust port 70 in the sleeve. The distal exhaust port 70 opens at a distal end of the sleeve 18 from the sleeve cavity 60 to the tank 22. In FIG. 4, the spool 16′ is in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the distal exhaust port 70 while the second fluid supply 48 provides fluid to the retarding chamber 38. However, it should be appreciated that when the spool 16 is “fully inserted,” the fluid can flow from the retarding chamber 38 through the distal exhaust port 70. The distal exhaust port 70 can axially communicate fluid through the spool 16′ and the spool cavity 68 and distal exhaust port 70 to an exhaust vent 72. The exhaust vent 72, can flow the fluid to the fluid tank 22 from which the fluid pump 20 can draw. That is, the distal exhaust port 70 can fluidly communicate with both the advancing port 56 and the retarding port 58 as well as with the fluid tank 22 drawn on by the fluid pump 20.

FIG. 5 depicts yet another implementation of a hydraulically-actuated VCT system 500. The system 500 includes a spool valve 14 having a spool 16 that is concentrically positioned relative to the sleeve 18 and is received within the sleeve cavity 60. The sleeve 18 can include an exhaust port 54 that is in fluid communication with the first fluid supply 46 and the second fluid supply 48. The exhaust port 54 can fluidly communicate with the advancing chamber 36 and the retarding chamber 38. A check valve 62 can be positioned in between the exhaust port 54 and the fluid supplies 46, 48. In FIG. 5, the spool is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the exhaust port 54 while the second fluid supply 48 provides fluid to the retarding chamber 38. The fluid leaving the exhaust port 54 can pass through the check valve 62 and be recirculated such that fluid leaving the advancing chamber 36 may be combined with fluid provided by the second fluid supply 48 to enter the retarding chamber 38. However, it should be appreciated that when the spool 16 is “fully inserted,” the fluid can flow from the retarding chamber 38 through the exhaust port 54 such that it is recirculated with fluid supplied by the first fluid supply 46 to the advancing chamber 36.

FIG. 6 depicts yet another implementation of a hydraulically-actuated VCT system 600. The system 600 includes a spool valve 14 having a spool 16 that is concentrically positioned relative to the sleeve 18 and is received within the sleeve cavity 60. The sleeve 18 can include an exhaust port 54 that is in fluid communication with the advancing chamber 36 and the retarding chamber 38. A check valve 62 can be positioned in between the exhaust port 54 and the fluid supplies 46, 48. In addition to fluidly communicating with the advancing chamber 36 and the retarding chamber 38, the exhaust port 54 can also be in fluid communication with the first fluid supply 46, the second fluid supply 48, and a fluid tank 22 via a vent conduit 74. In this way, a portion of the fluid exiting the advancing chamber 36 or the retarding chamber 38 can be recirculated to the other of the chamber 36, 38 being filled with fluid by one of the fluid supplies 46, 48 and another portion can be returned to the fluid tank 22 via the vent conduit 74. In FIG. 6, the spool 16 is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the exhaust port 54 while the second fluid supply 48 provides fluid to the retarding chamber 38, such that a portion of the fluid leaving the advancing chamber 36 is directed to the retarding chamber 38 and a portion is provided to the fluid tank 22 through the vent conduit 74. However, it should be appreciated that when the spool 16 is “fully inserted,” a portion of the fluid can flow from the retarding chamber 38 through the exhaust port 74 such that it is recirculated with fluid supplied by the first fluid supply 46 to the advancing chamber 36 and a portion is provided to the fluid tank 22.

FIG. 7 depicts yet another implementation of a hydraulically-actuated VCT system 700. In this implementation, the spool 16′ includes a spool cavity 68 with the spool exhaust port 78 that is selectively in fluid communication with the advancing chamber 36 and the retarding chamber 38. A distal exhaust port 70 opens at a distal end of the sleeve 18 to communicate fluid from the spool cavity 68 through the exhaust vent 72 to the tank 22. In addition to the distal exhaust port 70, the sleeve 18 includes the exhaust port 54 in fluid communication with the first fluid supply 46 and the second fluid supply 48 as well as the advancing chamber 36 and the retarding chamber 38. Check valves 62 can be positioned in between the exhaust port 54 and the fluid supplies 46, 48. A portion of the fluid exiting the advancing chamber 36 or the retarding chamber 38 can be recirculated to the other of the chamber 36, 38 being filled with fluid by one of the fluid supplies 46, 48 via the exhaust port 54. In FIG. 7, the spool 16′ is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the exhaust port 54 and the distal exhaust port 70 while the second fluid supply 48 provides fluid to the retarding chamber 38. However, it should be appreciated that when the spool 16′ is “fully inserted,” the fluid can flow from the retarding chamber 38 through the distal exhaust port 70 and the exhaust port 54. The distal exhaust port 70 can axially communicate fluid through the spool 16′ from the spool cavity 68 to a fluid tank 22 from which the fluid pump 20 can draw. The exhaust port 54 can communicate the fluid from the retarding chamber 38 to the advancing chamber 36.

FIG. 8 depicts yet another implementation of a hydraulically-actuated VCT system 800. The system includes a spool valve 14 having a spool 16 that is concentrically positioned relative to the sleeve 18 and is received within the sleeve cavity 60. The sleeve 18 can include an exhaust port 54 that is in fluid communication with the first fluid supply 46 and the second fluid supply 48 as well as the advancing chamber 36 and the retarding chamber 38. Two check valves 62 can be positioned in between the exhaust port 54 and the fluid supplies 46, 48. The fluid exiting the advancing chamber 36 or the retarding chamber 38 can be recirculated to the other of the chamber 36, 38 being filled with fluid by one of the fluid supplies 46, 48 through one of the check valves 62. In FIG. 8, the spool 16 is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the exhaust port 54 while the second fluid supply 48 provides fluid to the retarding chamber 38. However, it should be appreciated that when the spool 16 is “fully inserted,” a portion of the fluid can flow from the retarding chamber 38 through the exhaust port 54 such that it is recirculated with fluid supplied by the first fluid supply 46 to the advancing chamber 36 and a portion is provided to the fluid tank 22. Another implementation of a hydraulically-actuated VCT system 900 is shown in FIG. 9 that is similar to the implementation shown in FIG. 8. In FIG. 9, the exhaust port 54 is in fluid communication with two check valves 62 as well as a vent conduit 74 that fluidly communicates with a fluid tank 22. In this implementation, some of the fluid exiting the advancing chamber 36 or retarding chamber 38 through the exhaust port 54 can pass through one of the check valves 62 and flow into the chamber 36, 38 that is being filled with fluid and a portion of the fluid can flow to the fluid tank 22 through the vent conduit 74. Turning to FIG. 10, another implementation of a hydraulically-actuated VCT system 1000 is shown with the spool of system 700 and two check valves 62 in fluid communication with an exhaust port 74 formed in the sleeve 18. The spool 16′ includes a spool cavity 68 and spool exhaust port 78 that fluidly communicate with an exhaust vent 72 as described above.

In FIG. 11, another implementation of a hydraulically-actuated VCT system 1100 is shown. The system 1100 includes an exhaust port 54 that fluidly communicates with the advancing chamber 36 and the retarding chamber 38 through a chamber vent 76 having check valves 62 to recirculate fluid leaving one of the chambers 36, 38. In FIG. 11, the spool 16 is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the exhaust port 54 via the advancing port 56 while the second fluid supply 48 provides fluid to the retarding chamber 38. The fluid leaving the exhaust port 54 can be directed to the retarding chamber 38 through one of the check valves 62 in the chamber vent 76. When the spool 16 is in the “fully inserted” position relative to the sleeve 18, fluid can leave the retarding chamber 38 through the exhaust port 54 via the retarding port 58 while the first fluid supply 46 provides fluid to the advancing chamber 36. The fluid leaving the exhaust port 54 can be directed to the advancing chamber 36 through one of the check valves 62 in the chamber vent 76. FIG. 12 is another implementation 1200 of what is shown in FIG. 11, including an exhaust vent 72 in fluid communication with the chamber vent 76. In this implementation, the fluid leaving one chamber 36, 38 is directed through the exhaust vent 54 and a portion of the fluid flows into the other chamber 36, 38 and a portion flows through the exhaust vent 72 to the fluid tank 22.

FIG. 13 depicts another implementation of a hydraulically-actuated VCT system 1300. The system 1300 includes a sleeve 18 having an exhaust vent 54 and a spool 16 including a spool cavity 68 in fluid communication with a distal exhaust port 70 in the sleeve 18. The exhaust port 54 can fluidly communicate with the advancing chamber 36 and the retarding chamber 38 through a chamber vent 76 having check valves 62 to recirculate fluid leaving one of the chambers 36, 38. The spool 16′ can include the spool chamber 68 having a spool exhaust port 78 that fluidly communicates with the fluid tank 22 as described above. In FIG. 13, the spool 16′ is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through both the exhaust port 54 and the distal exhaust port 70 while the second fluid supply 48 provides fluid to the retarding chamber 38. The fluid leaving the advancing chamber 36 can enter the sleeve 18 at the advancing port 56 and leave the spool valve 14 via the exhaust port 54. The fluid can be directed to the retarding chamber 36 through one of the check valves 62 in the chamber vent 76. A portion of the fluid can leave the spool 16′ via the exhaust port 70 and flow to the fluid tank 22. When the spool 16′ is in the “fully inserted” position relative to the sleeve 18, fluid can leave the retarding chamber 38, pass through the retarding port 58 and leave the valve 14 through the exhaust port 54 while the first fluid supply 46 provides fluid to the advancing chamber 36. The fluid can be directed to the advancing chamber 36 through one of the check valves 62 in the chamber vent 76.

FIG. 14 depicts another implementation of a hydraulically-actuated VCT system 1400. The spool 16″ includes an elongated body and a spool cavity 68′ within the spool 16″ for receiving fluid from the first fluid supply 46, the second fluid supply 48, the advancing chamber 36, and the retarding chamber 38. The spool cavity 68′ can include a spool exhaust port 78 selectively in fluid communication with the advancing chamber 36 and the retarding chamber 38. The spool cavity 68′ can also include a check valve 62 to control the flow of fluid between the spool exhaust port 78 and the spool cavity 68′. In this implementation, the first fluid supply port 50 can fluidly communicate with the advancing chamber 36 while the second fluid supply port 52 can fluidly communicate with the retarding chamber 38. The spool exhaust port 78 can be moved to fluidly communicate with either the advancing port 56 or the retarding port 58. In FIG. 14, the spool 16″ is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the spool exhaust port 78 while the second fluid supply 48 provides fluid to the retarding chamber 38. The fluid entering the spool exhaust port 78 can be directed to the retarding chamber 38 through the check valve 62 in the spool cavity 68′. When the spool 16 is in the “fully inserted” position relative to the sleeve 18, fluid can leave the retarding chamber 38 through the spool exhaust port 78 while the first fluid supply 48 provides fluid to the advancing chamber 36. The fluid entering the spool exhaust port 78 can be directed to the advancing chamber 36 through the check valve 62 in the spool cavity 68′.

Turning to FIG. 15, another implementation of a hydraulically-actuated VCT system is shown 1500. The system 1500 includes a spool 16″ with a spool cavity 68′ within the spool 16″ for receiving fluid from the first fluid supply 46, the second fluid supply 48, the advancing port 56, and the retarding port 58. The sleeve 18 can include an exhaust port 54 that is in fluid communication with the fluid tank 22 via a vent conduit 74 as well as with the spool exhaust port 78. The spool cavity 68′ can include a check valve 62 to control the flow of fluid between the spool exhaust port 78 and the spool cavity 68′. In this implementation, the first fluid supply port 50 can fluidly communicate with the advancing chamber 36 and the second fluid supply port 52 can fluidly communicate with the retarding chamber 38. The exhaust port 54 and the spool exhaust port 78 can fluidly communicate with the advancing chamber 36 and the retarding chamber 38 as well as with a vent conduit 74. In FIG. 15, the spool 16″ is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the advancing port 50 and the spool exhaust port 78 while the second fluid supply 48 provides fluid to the retarding chamber 38. A portion of the fluid entering the spool exhaust port 78 can be directed to the retarding chamber 38 through the check valve 62 in the spool cavity 68′ while another portion leaves the spool valve 14 through the exhaust port 54 and vent conduit 74 flowing to the fluid tank 22. When the spool 16″ is in the “fully inserted” position relative to the sleeve 18, fluid can leave the retarding chamber 38 through the spool exhaust port 78 while the first fluid supply 46 provides fluid to the advancing chamber 36. A portion of the fluid entering the spool exhaust port 78 can be directed to the advancing chamber 36 through the check valve 62 in the spool cavity 68′ while another portion of the fluid flows out of the exhaust port 54 to the fluid tank 22.

FIGS. 16A and 16A depict other implementations of hydraulically-actuated VCT systems 1600. The system 1600 includes a sleeve 18 having one fluid supply port 50′ and one exhaust port 54 located axially between an advancing port 56 and a retarding port 58. The spool 16″ included with the system 1600 has a spool cavity 68′ within the spool 16 for receiving fluid from a single fluid supply 46′, an advancing port 56, and a retarding port 58 formed in the sleeve 18. The sleeve 18 can include an exhaust port 54 that is in fluid communication with the fluid tank 22 via a vent conduit 74. The spool cavity 68′ can include a check valve 62 to control the flow of fluid between the advancing port 56 or the retarding port 58 and the spool cavity 68′. In this implementation, the fluid supply port 50′ can fluidly communicate with the advancing chamber 36 or the retarding chamber 38. The exhaust port 54 can fluidly communicate with both the advancing chamber 36 and the retarding chamber 38 as well as the fluid tank 22 via the vent conduit 74. The exhaust port 54 also fluidly communicates with the spool exhaust port 78 in spool 16″. In FIGS. 16a and 16b , the spool 16″ is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the advancing port 56 while the fluid supply 50′ provides fluid to the retarding chamber 38. A portion of the fluid entering the spool exhaust port 78 can be directed to the spool cavity 68′ through the check valve 62 and flow to the retarding chamber 38 while another portion leaves the spool valve 14 through the exhaust port 54 and vent conduit 74 flowing to the fluid tank 22. When the spool 16″ is in the “fully inserted” position relative to the sleeve 18, fluid can leave the retarding chamber 38 through the retarding port 58 while the fluid supply 50 provides fluid to the advancing chamber 36. A portion of the fluid entering the spool cavity 68′ can be directed to the advancing chamber 36 through spool exhaust port 78 and the check valve 62 in the spool cavity 68′ while another portion of the fluid flows out of the exhaust port 54 to the fluid tank 22.

FIG. 17 depicts another implementation of a hydraulically-actuated VCT system 1700. The system 1700 includes a sleeve 18 having an advancing port 56 and a retarding port 58 located axially between a first fluid supply port 50 and a second fluid supply port 52. The spool 16″ has a spool cavity 68′ within the spool 16″ for receiving fluid from the first fluid supply 46, the second fluid supply 48, an advancing port 56, and a retarding port 58 formed in the sleeve 18. The spool cavity 68′ can include a first check valve 62 a and a second check valve 62 b to control the flow of fluid between the spool cavity 68′ and the advancing chamber 36 or the retarding chamber 38. In this implementation, the first fluid supply port 50 can fluidly communicate with the advancing chamber 36 and the second fluid supply port 52 can fluidly communicate with the retarding chamber 38. In FIG. 17, the spool 16″ is shown in a “fully withdrawn” position relative to the sleeve 18 such that fluid is leaving the advancing chamber 36 through the advancing port 56 while the second fluid supply 48 provides fluid to the retarding chamber 38. A portion of the fluid entering the advancing port 56 can be directed to the spool cavity 68′ through the spool exhaust port 78 and second check valve 62 b and flow to the retarding chamber 38. When the spool 16″ is in the “fully inserted” position relative to the sleeve 18, fluid can leave the retarding chamber 38 through the retarding port 58 while the first fluid supply 46 provides fluid to the advancing chamber 36. A portion of the fluid entering the spool cavity 68 can be directed to the advancing chamber 36 through the spool exhaust port 78 and the first check valve 62 a in the spool cavity 68. Another implementation of a hydraulically-actuated VCT system 1800 similar to what is shown in FIG. 17 is depicted in FIG. 18. The VCT system 1800 includes an exhaust port 54 in fluid communication with a fluid tank 22 such that a portion of the fluid leaving the advancing chamber 36 or the retarding chamber 38 can flow through the vent conduit 74 to the fluid tank 22. In some implementations, the vent conduit 74 can include a check valve 62, as is shown in FIG. 20.

Turning to FIG. 19, another implementation of a hydraulically-actuated VCT system 1900 is shown. The implementation shown in FIG. 19 is similar to what is shown and described with respect to FIGS. 17-18 and includes a fluid reservoir 80 in between the fluid tank 22 and the exhaust port 54. The other implementations described herein can incorporate the fluid reservoir 80.

It is to be understood that the foregoing is a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

As used in this specification and claims, the terms “e.g.,” “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. 

What is claimed is:
 1. A hydraulically-actuated variable camshaft timing (VCT) system, comp rising: a spool valve including a sleeve and a spool, having a plurality of radially-outwardly extending lands, received within the sleeve; a first fluid supply port in the sleeve configured to receive fluid from a fluid supply; a second fluid supply port in the sleeve configured to receive fluid from the fluid supply; an advancing port in the sleeve in fluid communication with an advancing chamber of a hydraulically-actuated camshaft phaser; a retarding port in the sleeve in fluid communication with a retarding chamber of the hydraulically-actuated camshaft phaser; and an exhaust port axially positioned in the sleeve in between the first fluid supply port and the second fluid supply port or in between the advancing port and the retarding port, wherein the exhaust port is configured to selectively receive fluid from either the advancing chamber or the retarding chamber depending on an axial position of the spool relative to the sleeve.
 2. The hydraulically-actuated VCT system recited in claim 1, further comprising a vent conduit that is in fluid communication with a fluid tank and the exhaust port.
 3. The hydraulically-actuated VCT system recited in claim 1, further comprising a spool cavity and a distal exhaust port in the sleeve that are in fluid communication with a fluid tank.
 4. The hydraulically-actuated VCT system recited in claim 1, further comprising a check valve in fluid communication with the exhaust port or a fluid pump.
 5. The hydraulically-actuated VCT system recited in claim 1, wherein the exhaust port is in fluid communication with the first fluid supply port and the second fluid supply port.
 6. The hydraulically-actuated VCT system recited in claim 1, further comprising a chamber vent that includes at least one check valve and fluidly communicates with the advancing chamber, the retarding chamber, and the exhaust port.
 7. The hydraulically-actuated VCT system recited in claim 1, further comprising a fluid reservoir in fluid communication with the exhaust port and a fluid tank.
 8. The hydraulically-actuated VCT system recited in claim 1, further comprising an exhaust vent in fluid communication with the exhaust port and a fluid tank.
 9. A hydraulically-actuated variable camshaft timing (VCT) system, comprising: a spool valve including a sleeve and a spool, having a plurality of radially-outwardly extending lands and a spool cavity, received within the sleeve; a first fluid supply port in the sleeve configured to receive fluid from a fluid supply; a second fluid supply port in the sleeve configured to receive fluid from the fluid supply; and a spool exhaust port included with the spool cavity that is positioned axially between the first fluid supply port and the second fluid supply port, wherein the spool exhaust port and the spool cavity are configured to selectively receive fluid from an advancing chamber of a hydraulically-actuated camshaft phaser or a retarding chamber the hydraulically-actuated camshaft phaser.
 10. The hydraulically-actuated VCT system recited in claim 9, further comprising a distal exhaust port vent in the sleeve that is in fluid communication with a fluid tank and the spool exhaust port.
 11. The hydraulically-actuated VCT system recited in claim 9, further comprising a check valve in the spool in fluid communication with the spool exhaust port.
 12. The hydraulically-actuated VCT system recited in claim 9, wherein the spool exhaust port is in fluid communication with the first fluid supply port and the second fluid supply port.
 13. The hydraulically-actuated VCT system recited in claim 9, further comprising a chamber vent that includes at least one check valve and fluidly communicates with the advancing chamber, the retarding chamber, and the spool exhaust port.
 14. The hydraulically-actuated VCT system recited in claim 9, further comprising a fluid reservoir in fluid communication with the spool exhaust port and a fluid tank.
 15. A hydraulically-actuated variable camshaft timing (VCT) system, comprising: a spool valve including a sleeve and a spool, having a plurality of radially-outwardly extending lands, received within the sleeve; a first fluid supply port in the sleeve configured to receive fluid from a fluid supply; a second fluid supply port in the sleeve configured to receive fluid from the fluid supply; an advancing port in the sleeve configured to receive fluid from an advancing chamber of a hydraulically-actuated camshaft phaser; a retarding port in the sleeve configured to receive fluid from a retarding chamber of a hydraulically-actuated camshaft phaser; and an exhaust port axially positioned in the sleeve in between the first fluid supply port and the second fluid supply port, wherein the exhaust port is configured to receive fluid through either the advancing port or the retarding port depending on an axial position of the spool relative to the sleeve.
 16. The hydraulically-actuated VCT system recited in claim 15, further comprising an exhaust vent that is in fluid communication with a fluid tank and the exhaust port.
 17. The hydraulically-actuated VCT system recited in claim 15, further comprising a check valve in fluid communication with the exhaust port.
 18. The hydraulically-actuated VCT system recited in claim 15, wherein the exhaust port is in fluid communication with the first fluid supply port and the second fluid supply port.
 19. The hydraulically-actuated VCT system recited in claim 15, further comprising a chamber vent that fluidly communicates with the advancing chamber, the retarding chamber, and the exhaust port.
 20. The hydraulically-actuated VCT system recited in claim 15, further comprising a fluid reservoir in fluid communication with the exhaust port and a fluid tank. 